U.S. patent number 10,632,963 [Application Number 15/704,635] was granted by the patent office on 2020-04-28 for load limiting seatbelt retractor.
This patent grant is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. The grantee listed for this patent is Ford Global Technologies, LLC. Invention is credited to Saeed David Barbat, S. M. Iskander Farooq, Mohammad Omar Faruque, Dean M. Jaradi.
United States Patent |
10,632,963 |
Faruque , et al. |
April 28, 2020 |
Load limiting seatbelt retractor
Abstract
A seatbelt retractor includes a spool, a piston, a cylinder, a
ring, and a valve. The spool is rotatably connected with a base by
the piston and the cylinder. The piston is fixed to one of the base
and the spool. The cylinder receives the piston and is fixed to the
other of the base and the spool. The piston and the cylinder define
a first chamber. The ring is sealed against the cylinder and
defines a second chamber connected with the first chamber by an
aperture. The valve is disposed across the aperture.
Inventors: |
Faruque; Mohammad Omar (Ann
Arbor, MI), Jaradi; Dean M. (Macomb, MI), Farooq; S. M.
Iskander (Novi, MI), Barbat; Saeed David (Novi, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
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Assignee: |
FORD GLOBAL TECHNOLOGIES, LLC
(Dearborn, MI)
|
Family
ID: |
65441480 |
Appl.
No.: |
15/704,635 |
Filed: |
September 14, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20190077366 A1 |
Mar 14, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60R
22/3413 (20130101); B60R 22/28 (20130101); B60R
2022/282 (20130101); B60R 2022/288 (20130101) |
Current International
Class: |
B60R
22/28 (20060101); B60R 22/34 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102009014999 |
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Sep 2010 |
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DE |
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102009033690 |
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Jan 2011 |
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DE |
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2016025780 |
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Feb 2016 |
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WO |
|
Primary Examiner: Kim; Sang K
Attorney, Agent or Firm: MacKenzie; Frank A. Bejin Bieneman
PLC
Claims
What is claimed is:
1. A seatbelt retractor comprising: a spool rotatably connected
with a base by a piston and a cylinder; the piston fixed to one of
the base and the spool; the cylinder receiving the piston, fixed to
the other of the base and the spool, defining a first chamber; and
a ring sealed against the cylinder and defining a second chamber
connected with the first chamber by an aperture; and a valve
disposed across the aperture.
2. The seatbelt retractor of claim 1, further comprising: a housing
with the spool rotatably coupled thereto for relative rotation of
the spool thereto about an axis of rotation defined by the spool;
and a base lock disposed between the base and the housing, the base
lock in a first condition fixing the base to the housing.
3. The seatbelt retractor of claim 2, the base lock further
comprising: a plurality of clutching teeth disposed on an outer
circumference of the base for rotation therewith; and an engagement
tooth connected to the housing, the engagement tooth in the first
condition being in engagement with the clutching teeth and the
engagement tooth in a second condition being not in engagement with
the clutching teeth, wherein engagement of the engagement tooth
with the clutching teeth rotatably fixes the cylinder to the
base.
4. The seatbelt retractor of claim 1, wherein the piston has piston
threads and the cylinder includes a bore receiving the piston and
cylinder threads are inside the bore and the piston threads and the
cylinder threads are in threaded engagement with each other.
5. The seatbelt retractor of claim 1, wherein the cylinder is
connected to the base and the piston is connected to the spool.
6. The seatbelt retractor of claim 1, wherein the ring is divided
into a plurality of secondary chambers, each with an aperture
connecting to the first chamber and a valve disposed across the
aperture.
7. The seatbelt retractor of claim 6, wherein the plurality of
secondary chambers is at least three.
8. The seatbelt retractor of claim 6, wherein the valves are
rupturable pressure relief valves having a rupture strength
corresponding to a predetermined seatbelt tension force.
9. The seatbelt retractor of claim 6, wherein the valves are
pressure relief valves and each has a predetermined pressure relief
value with its pressure relief value selected to correspond to an
associated predetermined seatbelt tension force, and the
predetermined seatbelt tension forces are not equal.
10. The seatbelt retractor of claim 9, wherein a flow area of the
apertures and the pressure relief value of the valves associated
with the apertures vary inversely, with the flow area of the
apertures decreasing as the pressure relief value of the valves
increases.
11. A seatbelt retractor comprising: a spool rotatably connected
with a base by an energy absorber; a housing with the spool
rotatably coupled thereto for relative rotation of the spool
thereto about an axis of rotation defined by the spool; a base lock
disposed between the base and the housing, the base lock in a first
condition fixing the base to the housing; and the energy absorber
including: a piston fixed to one of the base and the spool, a
cylinder receiving the piston and fixed to the other of the base
and the spool and defining a first chamber, and a ring sealed
against the cylinder and defining a second chamber connected with
the first chamber by an aperture; and a valve disposed across the
aperture.
12. The seatbelt retractor of claim 11, wherein the base lock
includes: a plurality of clutching teeth disposed on an outer
circumference of the base for rotation therewith; and an engagement
tooth connected to the housing, the engagement tooth in the first
condition being in engagement with the clutching teeth and the
engagement tooth in a second condition being not in engagement with
the clutching teeth, wherein engagement of the engagement tooth
with the clutching teeth rotatably fixes the cylinder to the
base.
13. The seatbelt retractor of claim 11, wherein the piston has
piston threads and the cylinder includes a bore receiving the
piston and cylinder threads are inside the bore and the piston
threads and the cylinder threads are in threaded engagement with
each other.
14. The seatbelt retractor of claim 11, wherein the ring is divided
into a plurality of secondary chambers, each with an aperture
connecting to the first chamber and a valve disposed across the
aperture.
15. The seatbelt retractor of claim 14, wherein the plurality of
secondary chambers is at least three.
16. The seatbelt retractor of claim 14, wherein the valves are
rupturable pressure relief valves having a rupture strength
corresponding to a predetermined seatbelt tension force.
17. The seatbelt retractor of claim 14, wherein the valves are
pressure relief valves and each has a predetermined pressure relief
value with its pressure relief value selected to correspond to an
associated predetermined seatbelt tension force, and the
predetermined seatbelt tension forces are not equal.
18. The seatbelt retractor of claim 17, wherein a flow area of the
apertures and the pressure relief value of the valves associated
with the apertures vary inversely, with the flow area of the
apertures decreasing as the pressure relief value of the valves
increases.
19. The seatbelt retractor of claim 11, wherein the cylinder is
connected to the base and the piston is connected to the spool.
20. The seatbelt retractor of claim 19, wherein an end cap is
rotatably fixed to the spool and to an end of the piston, and the
end cap is rotatably supported by a spring cover.
Description
BACKGROUND
The seatbelt portion of a vehicle restraint system secures the
occupant of a vehicle against harmful movement that may result from
a vehicle collision. The seatbelt functions to reduce the
likelihood of injury by reducing the force of occupant impacts with
vehicle interior structures. In this role the seatbelt applies
loads across the chest or lap of the occupant. Controlling or
reducing these loads may reduce the risk of occupant injury during
a collision. A seatbelt system may include a retractor that
incorporates a load limiting device. The retractor includes a spool
around which the webbing is wrapped. In the event of a vehicle
impact, the spool is locked, preventing its rotation and preventing
unwinding of the webbing. A load limiting mechanism within the
retractor allows control or reduction of restraint load transmitted
to the occupant during a vehicle impact. A known load limiting
mechanism includes a torsion bar disposed in a center of the spool.
The torsion bar may be a cylindrical bar of steel having a yield
strength selected to allow the bar to torsionally yield at a
predetermined value limiting the loads transmitted to the occupant,
thus reducing risk of injury during a vehicle impact. Twisting of
the torsion bar absorbs some of the inertia energy, thereby
reducing the load sustained by the occupant against the webbing.
The torsion bar, when plastically deformed, may yield in a
non-linear manner that may be difficult to duplicate. It is desired
to provide an improved load limiting mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a vehicle occupant with an example
seatbelt system.
FIG. 2 is a first perspective view of an example retractor.
FIG. 3 is a second perspective view of the example retractor of
FIG. 2.
FIG. 4 is an exploded view of the example retractor of FIGS. 2 and
3.
FIG. 5 is an enlarged perspective view of an example energy
absorber of the example retractor of FIG. 4.
FIG. 6 is a sectioned perspective view of the example energy
absorber of FIG. 5 with the section taken through a plane
coincident with the axis of rotation.
FIG. 7 is a sectional side view of an engagement mechanism in a
non-impact condition.
FIG. 8 is a sectional side view of the engagement mechanism of FIG.
7 in an impact condition.
FIG. 9A is a sectional downward view, through an imaginary cutting
plane 9 in the direction of arrows 9', of the energy absorber of
FIG. 5 in a first condition.
FIG. 9B is a sectional downward view of the energy absorber of FIG.
9A in a second condition.
FIG. 9C is a sectional downward view of the energy absorber of FIG.
9A in a third condition.
FIG. 9D is a sectional downward view of the energy absorber of FIG.
9A in a fourth condition.
FIG. 10 is a plot of force versus displacement of the energy
absorber of FIGS. 2-12.
DETAILED DESCRIPTION
Relative orientations and directions (by way of example, upper,
lower, bottom, forward, rearward, front, rear, back, outboard,
inboard, inward, outward, lateral, left, right) are set forth in
this description not as limitations, but for the convenience of the
reader in picturing at least one embodiment of the structures
described. Such example orientations are from the perspective of an
occupant seated in a seat, facing a dashboard. In the Figures, like
numerals indicate like parts throughout the several views.
A seatbelt retractor includes a spool, a piston, a cylinder, a
ring, and a valve. The spool is rotatably connected with a base by
the piston and the cylinder. The piston is fixed to one of the base
and the spool. The cylinder receives the piston and is fixed to the
other of the base and the spool. The piston and the cylinder define
a first chamber. The ring is sealed against the cylinder and
defines a second chamber connected with the first chamber by an
aperture. The valve is disposed across the aperture.
The seatbelt retractor may further include a housing and a base
lock. The spool may be rotatably coupled to the housing for
relative rotation thereto about an axis of rotation defined by the
spool. The base lock may be disposed between the base and a
housing. The base lock, in a first condition, fixes the base to the
housing.
A seatbelt retractor may include a spool, a housing, a base lock, a
base and an energy absorber. The spool may be rotatably connected
with the base by the energy absorber. The spool may be rotatably
coupled to the housing for relative rotation thereto about an axis
of rotation defined by the spool. The base lock may be disposed
between the base and the housing. The base lock in a first
condition may fix the base to the housing. The energy absorber may
include a piston, a cylinder, a ring and a valve. The piston may be
fixed to one of the base and the spool. The cylinder may receive
the piston and may be fixed to the other of the base and the spool.
The cylinder, with the piston, define a first chamber. The ring may
be sealed against the cylinder and may define a second chamber
connected with the first chamber by an aperture. The valve may be
disposed across the aperture.
The base lock may further include a plurality of clutching teeth
and an engagement tooth. The plurality of clutching teeth may be
disposed on an outer circumference of the base for rotation
therewith. The engagement tooth may be connected to the housing.
The engagement tooth, in the first condition, is in engagement with
the clutching teeth. The engagement tooth, in a second condition,
is not in engagement with the clutching teeth. Engagement of the
engagement tooth with the clutching teeth rotatably fixes the
cylinder to the base.
The piston may have piston threads. The cylinder may include a bore
receiving the piston. Cylinder threads may be inside the bore. The
piston threads and the cylinder threads may be in threaded
engagement with each other.
The cylinder may be connected to the base and the piston may be
connected to the spool.
The ring may be divided into a plurality of secondary chambers,
each with an aperture connecting to the first chamber and a valve
disposed across the aperture.
The plurality of secondary chambers may be at least three.
The valves may be rupturable pressure relief valves having a
rupture strength corresponding to a predetermined seatbelt tension
force.
The valves may be pressure relief valves and may each have a
predetermined pressure relief value. The pressure relief value of
each may be selected to correspond to an associated predetermined
seatbelt tension force. The predetermined seatbelt tension forces
are not equal.
A flow area of the apertures and the pressure relief value of the
valves associated with the apertures may vary inversely, with the
flow area of the apertures decreasing as the pressure relief value
of the valves increases.
An end cap may be rotatably fixed to the spool and to an end of the
piston. The end cap may be rotatably supported by a spring
cover.
An example restraint system 20, as illustrated in FIGS. 1-10, may
be disposed in a vehicle 22. The vehicle 22 includes a seat 24 that
may support an occupant 26 of the vehicle 22. The seat 24 may be a
front seat or a rear seat, and may be in any cross-vehicle
position. The seat 24 shown in FIG. 1 is a bucket seat, but
alternatively the seat 24 may be a bench seat or another type of
seat. The occupant 26 may be an adult or adolescent, or may
alternatively be a child car seat for supporting an infant or young
child. The position and orientation of the seat 24 and components
thereof may be adjustable by the occupant 26.
The restraint system 20 includes an example seatbelt system 28 and
may also include an airbag system (not shown). The illustrated
seatbelt system 28 is a three-point system. By three-point, it is
meant that a seatbelt, i.e., a webbing or a belt, 30 of the system
28 restrains the occupant 26 at three points: at a shoulder, in the
example of FIG. 1 the right shoulder, and on both sides of the
occupant's lap.
The seatbelt system 28 may include, in addition to the seatbelt 30,
a retractor 32, a D-ring 34, a seatbelt latch plate 36, an anchor
(not shown), a buckle 38, and a buckle mount 40. The seatbelt
system 28 may, alternatively, include another arrangement of
attachment points. The seatbelt system 28, when fastened, retains
the occupant 26 on the seat 24, e.g., during sudden decelerations
of the vehicle 22.
The retractor 32 receives and dispenses a first end of the seatbelt
30. The retractor 32 may be fixed, as illustrated, to the vehicle
structure, e.g., to a B-pillar 42, or alternatively, to a frame of
the seat 24. An alternative vehicle structure location includes a
floor of the vehicle 22.
The D-ring 34 provides a consistent orientation of the seatbelt 30
across the occupant's shoulder, e.g., in a back of the seat 24. The
D-ring 34, when included, receives the seatbelt 30 and directs the
seatbelt 30 from the retractor 32 across the shoulder of the
occupant 26. The D-ring 34 may be fixed to the back of the seat 24,
or, alternatively, to a structural component of the vehicle, e.g. a
B-pillar 42. When the retractor 32 is mounted to one of the
B-pillar 42 and the seat frame, the D-ring 34 may be omitted from
the system 28.
The seatbelt latch plate 36, i.e., a clip, selectively engages the
buckle 38 on an inboard side of the occupant 26. The latch plate 36
is received by a slot in the buckle. The buckle 38 is fixed to the
vehicle structure or to the seat frame by the buckle mount 40.
The seatbelt anchor may be in the form of an anchor plate (not
shown) and may be disposed on an outboard side of the seat 24. The
plate is fixed to a second end of the seatbelt 30 opposite the
retractor 32 and is also fixed to one of the frame of the seat 14
and the structure of the vehicle 12 to thereby fix the second end
of the seatbelt 30.
The latch plate 36 slides freely along the seatbelt 30 and, when
engaged with the buckle 38, divides the seatbelt 30 into a lap band
44 and a shoulder band 46. The lap band 44 is disposed between the
latch plate 36 and the anchor. The shoulder band 46 may be disposed
between the latch plate 36 and the D-ring 34.
With reference to the FIGS. 2-10 the example retractor 32 includes
a housing 48, a spool 50, a retractor spring 52, a disc 54, a base
56, a base lock 58, a spring cover 60, and a lock cover 61. The
spool 50 is rotatably coupled to the housing 48 for relative
rotation thereto about an axis of rotation 62 defined by the spool
50. The spool 50 is rotatably connected with, i.e., rotatably fixed
for rotation with, the base 56 by an energy absorber 63.
The lock cover 61 is fixed to the housing 48 at the second end of
the spool 50 and is disposed over the base 56 and the lock 58. The
illustrated lock 58, best shown in FIGS. 7 and 8, may include
components fixed to either the housing 48 or the lock cover 61.
The spool 50 may freely rotate relative to the housing 48. The
first end of the seatbelt 30 is connected to the spool 50. The
spool 50 includes a hub 64 that may be cylindrical in shape and
centered on the axis 62. The spool 50 may be adapted to receive the
seatbelt 30, for example, by including a webbing attachment slot 65
and permitting the seatbelt 30 to wind around the hub 64 of the
spool 50.
The seatbelt 30 may be attached to the spool 50. Specifically, one
end of the seatbelt 30 may be attached to the seatbelt anchor, and
another end of the seatbelt 30 may be attached to the spool 50,
with the seatbelt 30 wound around the spool 50 beginning at that
end. The seatbelt 30 may be formed of a fabric in the shape of a
strap.
The spool 50 may include a first spool flange 66 at a first end of
the hub 64 and a second spool flange 68 at a second end of the hub
64. The flanges 66, 68 may provide a border for the seatbelt 30,
helping to maintain the layers or wraps of the seatbelt over the
hub 64 in alignment with each other.
The retractor spring 52 rotatably biases the spool 50 relative to
the housing 48. The retractor spring 52, as noted above, may extend
from the housing 48 to the spool 50 either directly or indirectly,
e.g., through the disc 54 and the cover 60. The retractor spring 52
may be loaded in tension or compression when the seatbelt 30 is
fully retracted, and the retractor spring 52 may be further loaded
in either tension or compression when the seatbelt 30 is extended
from the spool 50. Thus, the retractor spring 52 may exert a force
tending to retract the seatbelt 30. The retractor spring 52 may be
a spiral torsion spring or any other suitable type of spring. The
spring cover 60 is fixed to the housing 48 at a first end of the
spool 50, provided by the first spool flange 66, and is disposed
over the disc 54 and the spring 52. The spring cover 60 may include
a support sleeve 70 that receives a spindle portion 71 of an end
cap 72 for rotatable support of the spool 50. The end cap 72 may be
fixed to the spool 50 in any appropriate manner to ensure unitary
movement therewith, e.g., by welding.
The housing 48 may be formed of stamped sheet steel or other
suitably rigid material, e.g., plastic. The housing 48 may include
a center portion 74 connecting a first wing 76 and a second wing
78. The first wing 76 and the second wing 78 are on opposite sides
of the center portion 74 and face each other. The wings 76, 78
receive the spool 50, with the flanges 66, 68 being disposed
between the wings 76, 78. The housing 48 may be mounted to a
structural element of the vehicle 22, e.g., to the B pillar 42 in
the instance the seat 24 is a front seat, to a C pillar (not shown)
when the seat 24 is a rear seat, or may be mounted to the seat
24.
The energy absorber 63 includes a piston 80, a cylinder 82 and a
ring 84. The piston 80 is fixed to one of the base 56 and the spool
50. The example illustrated piston 80 is fixed to the spool 50 via
the endcap 72 as described in more detail below. The cylinder 82 is
fixed to the other of the base 56 and the spool 50. The example
illustrated cylinder 82 is fixed to the base 56 as described in
more detail below.
The cylinder 82 has a threaded bore 83 that threadingly receives
the piston 80. The cylinder 82, together with the piston 80, and
more particularly a closed first end 86 of the piston 80, define a
first chamber 88 within the bore 83 of the cylinder 82. A
substantially incompressible liquid 90 is disposed in the first
chamber 88. The liquid 90 may fill the chamber 88. Rotation between
the piston 80 and the cylinder 82, with the threaded engagement
therebetween, displaces the piston 80 into the cylinder 82,
compressing the liquid 90 therein.
The ring 84 circumscribes and is fixed to the cylinder 82. The ring
84 defines a second chamber 92, represented collectively by
reference numbers 92A, 92B and 92C, with respect to the cylinder
82. The structure of the energy absorber 63 and its operation is
described in more detail below.
The spool 50 is, as noted above, rotatably coupled to the housing
48 for relative rotation thereto. The piston 80 is fixed on a
second end 94 to the end cap 72 for rotation therewith. The end cap
72 may be rotatively fixed to the second end 94 by axially oriented
outer splines 96 on the second end 94 that may be received by
complementary inner splines 98 formed inside of the end cap 72.
The first spool flange 66 may include a flange aperture 100 having
splines (not shown) complementary to the outer splines 96,
facilitating the unitary rotation of the spool 50, the end cap 72,
and the piston 80. The example disc 54 may be fixed to the first
spool flange 66 for rotation with the spool 50.
The first end 86 of the piston 80 has threads 102, i.e., piston
threads, thereon. The second end 94 is threaded into a first end
104 of the cylinder 82 which has receiving threads 106, i.e.,
cylinder threads, inside the threaded bore 83 that are
complementary to the threads 102. The piston threads 102 are in
threaded engagement with the cylinder threads 106. A shank 107 of
the piston 80 between the threads 102 and the second end 94 may
have an outside diameter equal to or less than a minor diameter of
the threads 102 to allow the piston 80 to thread into the cylinder
bore 83 to a depth greater than the threads 102. Alternatively, the
threads 102 may extend an entire length of the piston 80 or to the
outer splines 96.
A flow control aperture 108, generic to each of flow control
apertures 108A, 108B and 108C and represented in the figures
thereby, may pass through a wall 109 of the cylinder 82, connecting
the first chamber 88 and the second chamber 92. A rupturable
pressure relief valve 110, generic to each of rupturable pressure
relief valves 110A, 110B, and 110 C and represented in the figures
by the reference numbers 110A, 110B and 110C, is disposed across
the flow control aperture 108, blocking the liquid 90 from moving
from the first chamber 88 to the second chamber 92.
The rupturable valve 110 has a rupture strength of a first
predetermined pressure P1, corresponding to F1 for a given piston
area and an associated predetermined seatbelt tension force. The
exact nature of the valve may be varied. An example valve is
illustrated in U.S. Pat. No. 3,007,773. The valve 110 may
alternatively be in the form of a membrane configured to rupture at
a predetermined pressure.
When the valve 110 ruptures, the liquid 90 may flow from the first
chamber 88 into the second chamber 92. A rate of flow of the liquid
90 from the first chamber 88 to the second chamber 92 corresponding
to an axial speed of the piston 80 within the chamber 88, and to
the rate of displacement of the seatbelt 30 from the spool 50. A
size, i.e., a flow area, of the aperture 108 may affect a pressure
of the liquid 90 within the first chamber 88 as the piston 80 is
being driven against it, controlling a resistance to displacement
of the piston 80 within the bore 83. Thus, the reactive force of
the liquid 90 against the piston 80 varies with the displacement
rate of the piston 80 and the size, i.e., flow area, of the flow
control aperture 108. The reactive force may be tuned to achieve a
desired cushioning of the seatbelt 30 against the occupant 26.
Tuning of a maximum force and a desired rate of force increase may
be achieved by varying system parameter including a thread pitch
and the flow control aperture 108 size as to achieve a desired
seatbelt reaction force.
The second chamber 92 may include a plurality of second, i.e.,
secondary, chambers, e.g., first secondary chamber 92A, second
secondary chamber 92B and third secondary chamber 92C distributed
radially about and extending from the cylinder 82. Three blocking
walls 111A, 111B and 111C may be used to separate the secondary
chambers 92A, 92B and 92C. The walls 111A, 111B and 111C may be
disposed within and constitute part of the ring 84. The walls are
sealed against an inside surface of the ring 84 and against the
cylinder 82.
Each of the secondary chambers 92A, 92B and 92C may be connected to
the first chamber 88 by a distinctively sized first, second and
third flow control apertures 108A, 108B and 108C passing through
the cylinder wall 109. Each of the apertures 108A, 108B and 108C
may have a unique size, i.e., flow area.
The apertures 108A, 108B and 108C may respectively be covered by
first, second and third valves 110A, 110B and 110C respectively,
each having a unique predetermined pressure relief value,
corresponding to a belt tension, selected for use with the
associated secondary chamber 92A, 92B, 92C.
Providing the three secondary chambers 92A, 92B and 92C with
distinctive aperture sizing and distinctive valve rupture values
allows for a stair-step increase in loading responsive to a
seatbelt force when the spool is locked, as described in more
detail below. Additionally, for alternative tuning demands, all
three flow control apertures 108A, 108B and 108C may connect to a
single common second chamber 92 as may be provided by the ring 84
without walls 111A, 111B and 111C. The second end 94 may also form
a side of the ring 84.
The base 56 may be in the form of a disc. The cylinder 82 is fixed
on a second end 112 to the base 56 for rotation therewith. The
second end 112 may be rotatively fixed to the base 56 by axially
oriented outer splines 114 on the second end 112 that may be
received by complementary inner splines 116 formed inside of an
aperture 118 in the base 56.
The base lock 58 may be any mechanism suited to preventing or
restricting rotation of the base 56 or the spool 50 relative to the
housing 48. Such mechanisms as lock 58 are known and are
commercially available from companies including Autoliv Inc. and Z
F Friedrichshafen AG. One type of base lock may engage the cylinder
82 with the housing 48 responsive to a rapid movement of the
webbing 30 and an associated rapid spinning of the spool 50.
Another type of base lock, consistent with the illustrated base
lock 58, may engage the base 56 with the housing 48 responsive to a
sudden deceleration or rearward acceleration of the vehicle 22. It
is also known to incorporate both types of mechanisms into a single
retractor 32. The example base lock 58 is just one approach to
engaging the base 56 with the housing 48. The example base lock 58
includes axially extending clutching teeth 120 disposed around an
outer circumference of the base 56 and an example base lock 58 that
engages the clutching teeth 120 under predetermined conditions.
The base lock 58 may include a pivot arm 124 pivotable relative to
a ball retainer 126. The ball retainer 126 includes a first ball
track 128, and is fixed relative to the housing 48. The pivot arm
124 includes a second ball track 130 facing the first ball track
128. The pivot arm 124 also includes an engagement tooth 132 on a
side opposite the second ball track 130. Via the pivot arm 124, the
tooth 132 is connected with the housing 48. In an installed
position, the tracks 128, 130 are parallel with a forward direction
of motion of the vehicle 22. A ball 134, e.g., a steel ball, is
disposed in the tracks 128, 130. A hinge 136, allowing pivotable
movement of the pivot arm 124 relative to the ball retainer 126, is
at a rear of the tracks 128, 130.
In a first position, the tooth 132 and the pivot arm 124 are
pivoted downwardly, ensuring that there is no engagement between
the tooth 132 and the clutching teeth 120. Also in the first
position, associated with the ball 134 being in a rearward position
on the tracks 128, 130, as illustrated in FIG. 7, a distance
between forward ends of the tracks 128, 130 is less than a diameter
of the ball 134. An unwinding direction of rotation of the spool 50
is indicated by an arrow 138. Rotation of the spool 50 in the
direction of arrow 138 results in the webbing 30 unwrapping from
the spool 50, and being dispensed from the retractor 32.
In a second position, the tooth 132 and pivot arm 124 are pivoted
upwardly, toward the base 56 and the tooth 132 into engagement with
the clutching teeth 120. In the second position, associated with
the ball 134 being in a forward position on the tracks 128, 130, as
illustrated in FIG. 8, a distance between forward ends of the
tracks 128, 130 is greater than the distance of the first
position.
A pivot spring 140 may be disposed between the pivot arm 124 and
the ball retainer 126 to bias the pivot arm 124 toward a disengaged
position, i.e., an unlocked condition. The biasing of the pivot arm
124 downward may also bias the ball 134 to the disengaged
position.
The second ball track 130 has a first portion in a first position
relatively proximate to the hinge 136. With the base lock 58 in a
locked condition, i.e., with the engagement tooth 132 of pivot arm
124 engaging the clutching teeth 120, the base 56 is fixed relative
to the housing 48.
The seatbelt retractor 32 operates as described below and as
illustrated in FIG. 10 and FIGS. 9A-9D. FIGS. 9A-9D are sections
taken through an intersection of the energy absorber 63 with an
imaginary plane 9 in the direction of arrows 9'.
FIG. 10 is a graph 142 of a curve 144A describing an example
relationship between a displacement of the seatbelt 30 from the
spool 50 in the unwinding direction 138 and a seatbelt force
resisted by the energy absorber 63. The horizontal axis is labeled
"Displacement (Belt payout)", but may alternatively be labeled
"spool rotations" or "piston displacement" as there is a
substantially linear relationship between all three values. The
vertical axis is labeled "Belt Force", but may alternatively be
labeled "spool torque" or "piston pressure", as there is a
substantially linear relationship between all three values.
In the event of a frontal impact, the occupant 26 of the front seat
24 has forward momentum relative to the rest of the vehicle 22.
Likewise, the ball 134 of the base lock 58 has forward momentum
relative to the ball retainer 126 and the pivot arm 124. An
associated forward motion of the ball 134 along tracks 128, 130
pivotably displaces pivot arm 124 against the torque of pivot
spring 140 and away from retainer 126. The pivoting of pivot arm
124 brings engagement tooth 132 into engagement with the clutching
teeth 120 of the base 56, preventing further rotation of the
cylinder 82 relative to the housing 48.
The forward inertial motion of the occupant 26, and particularly of
the upper torso of the occupant 26, may act against the webbing 30.
With rotation of the base 56 prevented by engagement of the tooth
132 with teeth 120, an inertial force of the occupant against the
webbing 30, and particularly the shoulder band 46, is resisted by
the spool 50 of the retractor 32.
Consistent with the embodiment of FIGS. 2-9D, preventing rotation
of the base 56 does not immediately prevent rotation of the spool
50 and further dispensing of the webbing 30 from the retractor 32
when the spool 50 is resisting a predetermined magnitude of
passenger inertia. Rotation of the spool 50 when the base 56 is
locked rotates the piston 80 relative to the cylinder 82, threading
the piston 80 deeper into the cylinder 82.
The graph 142 is consistent with the description of the operation
of the system 20 and its associated curves 144A, 144B and 144C. The
stair-step appearance of a baseline curve 144A associated with a
first speed, i.e., velocity of the piston 80 in the axial
direction, is explained by a sequential transfer of liquid 90 from
the first chamber 88 to the secondary chambers 92A, 92B, 92C. Each
secondary chamber 92A, 92B, 92C is connected to the first chamber
88 by is associated aperture 108A, 108B and 108C, with flow
initially being restricted by valves 110A, 110B, 110C. Each of the
secondary chambers 92A, 92B, 92C has a limited volume, e.g., one
third of the available volume of liquid 90 in the unstressed first
chamber 88, and each aperture 108A, 108B and 108C is sealed with
its associated rupturable valve 110A, 110B, 110C respectively.
The valves 110A, 110B, 110C are configured, i.e., formed of a
selected material to a predetermined shape, to rupture at
progressively higher pressures/piston forces. For example, the
valve 110A for the first secondary chamber 92A may be designed to
rupture at a first predetermined seatbelt tension force of F1, the
valve 110B of the second secondary chamber 92B at a second
predetermined seatbelt tension force F2, and the valve 110C of the
third secondary chamber 92C at a third predetermined seatbelt
tension force F3, with F3>F2>F1. For example, F3 may equal
three times the value of F1, and F2 may equal two times the value
of F1.
Following the example first or baseline curve 144A, the seatbelt
tension, i.e. belt force, associated with the pressure within the
first chamber 88, increases from a starting point of zero with an
initial displacement from a starting point, i.e., zero, for the
seatbelt 30 and the piston 80. The initial steep increase in force
with very little increase in displacement is due to compression of
the liquid 90 in the first chamber 88 prior to rupture, i.e.,
opening, of the first valve 110A at F1. The slope is substantially
a function of a modulus of elasticity of the liquid 90. The belt
force, at a first rate of piston displacement, substantially
plateaus at a value of F1, as the liquid 90 flows past the ruptured
valve 110A (not illustrated in a ruptured condition), through the
first flow control aperture 108A, and into the first secondary
chamber 92A.
When the first secondary chamber 92A is filled at V1, the belt
force again increases rapidly until the second valve 110B ruptures
at belt force F2. The second flow control aperture 108B to the
second secondary chamber 92B is more restrictive than the first
flow control aperture 108A connecting the second secondary chamber
92B with the first chamber 88, yielding a slope of the force as a
function of the displacement coinciding with the liquid 90 entering
the second secondary chamber 92B, greater than the slope associated
with the liquid 90 entering the first secondary chamber 92A. As
such, a flow area of aperture 108A may be greater than a flow area
of aperture 108B.
When the second secondary chamber 92B is filled, at line V2, the
force resumes its rapid ascent, with the liquid 90 in the first
chamber 88 being further compressed until the valve 110C across the
aperture 108C for the third secondary chamber 92C ruptures. As the
aperture 108C to the third secondary chamber 92C is more
restrictive than the aperture 108B to the second secondary chamber
92B, the slope of the belt force as a function of belt
displacement, associated with the entry of the liquid 90 into the
third secondary chamber 92C, is steeper than the slope associated
with the liquid 90 entering the second secondary chamber 92B. As
such, a flow area of aperture 108B may be greater than a flow area
of aperture 108C. Once the third secondary chamber 92C is full, the
slope increases rapidly, as the liquid 90 remaining in the bottom
of the first chamber 88 has nowhere else to go.
For systems 20 employing a plurality of secondary chambers 92, the
flow area of the apertures 108 and the pressure relief value of the
valves 110 associated with the apertures 108 may vary inversely,
with the flow area of the apertures 108 decreasing as the pressure
relief value of the valves 110 increases.
Arrow 146 indicates a direction of increasing piston speed. A
second curve 144B, below the baseline curve 144A, representing a
first or baseline piston speed, i.e., belt speed, illustrates an
example force-displacement relationship for a slower piston/belt
speed. Curve 144C, above the baseline curve 144A, illustrates an
example force-displacement relationship for a faster piston/belt
speed than that associated with the baseline curve 144A. The
force-displacement relationship varies with the speed of the
displacement when the liquid 90 is being displaced through the
apertures 108A, 108B, 108C. The rupture forces will not be
significantly affected by the speed of the piston 80 or belt 30,
and the force-displacement ratio when the liquid 90 is being
compressed, but not displaced through the apertures 108A, 108B,
108C, will not be affected by the speed of the piston 80.
The additional webbing 30 dispensed by the retractor 32 from the
spool 50 may be that corresponding to substantially two revolutions
of the spool 50 after engagement of the tooth 132 with the teeth
120, e.g., approximately 8-10 inches.
The magnitude of available rotation, and thus an amount of webbing
30 payed out, may be controlled by factors including an inertia
energy of the occupant 26 being restrained, a pitch of the threads
102, 106 and an available amount of piston 80 to base 56 travel.
Piston 80 to base 56 travel may in turn be affected by additional
factors including: a depth of the bore 83, and the geometric
characteristics of the ring 84 determining the available volumes of
the secondary chambers 92A, 92B and 92 C.
A substantial termination of spool 50 rotation occurs when a torque
resulting from the seatbelt force is exceeded by a torque needed by
the ring 84 to displace additional liquid 90 into the secondary
chambers 92A, 92B, 92C from the first chamber 88. Some of the
occupant's forward inertia energy is absorbed by displacement of
liquid 90, thus reducing the force imparted by the webbing 30
against the occupant 26 when the webbing 30 stops during an
incident such as a frontal impact.
After an impact in which the valves 110A, 110B, 110C of the energy
absorber are ruptured, the retractor 32 may be replaced with a
replacement retractor 32.
As used herein, the adverb "substantially" means that a shape,
structure, measurement, quantity, time, etc. may deviate from an
exact described geometry, distance, measurement, quantity, time,
etc., because of imperfections in materials, machining,
manufacturing, transmission of data, computational speed, etc.
The disclosure has been described in an illustrative manner, and it
is to be understood that the terminology which has been used is
intended to be in the nature of words of description rather than of
limitation. Many modifications and variations of the present
disclosure are possible in light of the above teachings, and the
disclosure may be practiced otherwise than as specifically
described.
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